This application claims the priority of Korean Patent Application No. 2003-77790, filed on Nov. 4, 2003, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference.
1. Field of the Invention
The present invention relates to a slim optical pickup, and more particularly, to a slim optical pickup in which a leaf spring is combined with an upper surface of a semiconductor substrate. The semiconductor substrate is a silicon optical bench (SiOB) monolithically manufactured with a photodetector.
2. Description of the Related Art
Recently, the use of mobile information devices, such as personal digital assistants (PDA), mobile phones, digital cameras, and camcorders has increased rapidly. To record and reproduce data to and from a mobile information device, an optical pickup device is required. To apply an optical pickup device to the mobile information device, research on the miniaturization and slimness of the optical pickup device is being actively conducted.
FIG. 1 is a perspective view illustrating a combined SiOB and leaf spring, in which a light source and optical devices are integrated, for use in a conventional slim optical pickup. FIG. 2 is a cross-sectional view illustrating a conventional slim optical pickup to which the silicon optical bench and the leaf spring of FIG. 1 are applied.
Referring to FIGS. 1 and 2, a slim optical pickup 10 comprises a silicon optical bench (SiOB) 30 in which a light source 12, such as a laser diode, a monitoring photodetector 34, a sloped mirror 14, and a photodetector 38 are included; a polarized light beam splitter 16; a prism 19 which includes first and second reflection surfaces 13 and 18; spacers 15 and 17 disposed between main substrate 32 and beam splitting 16/prism 19; a hologram optical element (HOE) 20; an objective lens 26 attached to a backside of a predetermined part of a SiOB 30 to face the HOE 20; aperture 24 in main substrate 32; a leaf spring 40 attached to a backside of the SiOB 30; and a heat sink 50 disposed on a surface of the leaf spring 40. Wiring 36 electrically connects photodetector 38 to a bonding pad 33. In FIG. 2, 11 corresponds to monitoring mirror 111 described below.
FIG. 3 is a cross-sectional view illustrating a method of electrically connecting a semiconductor substrate to a leaf spring when assembling a conventional slim optical pickup.
Referring to FIG. 3, the conventional slim optical pickup 10 has a structure of combining the leaf spring 40 on the back surface of the SIOB 30. In this conventional structure, when wire bonding wire 62 from a bonding pad 33 of the SiOB 30 to a bonding pad 44 formed on the leaf spring 40, a gap between a side surface of the SiOB 30 and the bonding pad 44 of the leaf spring 40 must be maintained to at least 0.5 mm due to a thickness of a capillary of a wire bonder 60.
In this case, a space with a width equal to the width of the bonding pad, plus 0.5 mm on each side of the SiOB 30, is required. Accordingly, there is a drawback in that the width of the leaf spring 40 has to be increased due to the protruded portion corresponding to the space of the leaf spring 40 which is equal in width to the bonding pad plus 0.5 mm on each side.
As a result, there is a heavy load on a motor due to the weight of the head, thereby increasing the power consumption of the motor and increasing seeking time.
In a slim optical pickup, most of the heat is generated from a light source 12 composed of a laser diode. Therefore, it has been known that it is effective to attach a heat sink 50 on a back side of the SiOB 30 since the heat generated is transmitted through a main substrate 32, which is formed of silicon.
However, since the heat generated from the light source 12 finally reaches the heat sink 50 after sequentially passing through the main substrate 32 of the SIOB 30, an adhesive 39 bonding the main substrate 32 to the leaf spring 40, the leaf spring 40, and an adhesive 49 bonding the leaf spring 40 to the heat sink 50, this structure has lower heat transfer efficiency than a structure in which the heat sink is attached to the back side of the SiOB 30. Therefore, there is a problem in that heat cannot be dissipated effectively.